Salamanders

Most every first grader knows about frogs and toads and their life cycles. And, if they know about amphibians, they may know that salamanders are part of this group too. But rarely do they talk about salamanders and get to see them up close.

This month in the K-2 Program, BRDC staff read excerpts from a youth salamander guidebook discussing the differences between salamanders and lizards (amphibians vs reptiles) and some of the features of our local salamanders, where they live, their habitats, and how they breathe. We also brought in some live, local salamanders for the kids to observe.

Our focus was on the Eastern hellbender, our largest salamander. After watching a video on the hellbender, we discussed ways to save and protect this amazing salamander and have him swimming in our rivers and streams for future generations. 

Bullfrog tadpoles or not?

Tadpoles can be tough to identify and I do not often have the patience to count tooth rows or such. I netted some tadpoles yesterday at one of our ponds where I know that both bullfrogs and green frogs are present. I only know for certain that bullfrogs have bred here. Many of the older tadpoles (see photos) show distinct black spots. If I recall correctly, such punctate, clearly defined spots are characteristic of bullfrog tadpoles, not green frogs.Does anyone else have similar or different experiences?

Bill Dunson, Galax

Beware the red eft

While on one of my daily nature walks I looked down and spotted one of the true beauties of the woods, a red eft (see photo). They wander around, especially after rains and are very slow-moving and unafraid. Of course there is a reason for this- they are protected by a very potent poison, tetrodotoxin. You cannot be poisoned by handling the young newt, but if you eat it your nerve cells will have some severe problems. The bright orange/red coloration of red efts, which are juvenile stages of the red-spotted newt, clearly warns potential predators to leave them alone. As the red efts mature into adults, they become more greenish-yellow (see second photo). The adults return to the water where the gilled larvae started life and spend the rest of their lives there. This "reverse" life history (embryos, gilled larvae and adults are aquatic, but juveniles are terrestrial) is in contrast to typical amphibians, where only the embryos and larvae are aquatic. While there is much about this process that is unclear, it does seem likely that such an alternation of generations between habitats is probably a means of minimizing competition for limited food resources. One strange thing is that not all populations of newts have an eft stage, perhaps due to unsuitability of land habitats or less competition for food in the water. A similar phenomenon may cause retention of gills in some populations of tiger salamanders (leading to presence of aquatic, reproductively adult axolotls that resemble gilled larvae).

Another really interesting feature of red efts is that they are probably mimicked by other amphibians such as the red salamander (see photo). This latter creature is apparently tasty but may be protected by its resemblance to the very toxic red eft. Isn't it intriguing how the color red has come to be used as both a warning and an attractant, for example as the prime color for flowers used for nectar by hummingbirds, and as the color of ripe fruits? Remember also that the recognition of the color red requires that an animal has color vision, which many mammals do not. So the target predators for this red-hued message by the efts is likely to be birds.

Here we have another example of the complex interactions that govern the lives and appearance of critters- just amazing!

-Bill Dunson

Galax, VA & Englewood, FL

The enigmatic life & death of toad tadpoles

One of our favorite places

to stop while traveling through GA is the Botanical Garden in Athens. Now I hope we may be forgiven for revealing that we do not always focus entirely on the fabulous plants, both exotic and native that are on display there. Indeed we enjoy those but the garden is somewhat unusual in that it includes some very nice deciduous and flood-plain forests. So in the Spring you can expect to find some interesting migrating birds.

While my wife was chasing

after a Kentucky warbler calling from the bushes along a power-line cut, I noticed something strange in a drying pond, a mass of wriggling black objects (see photo 1).

On closer inspection (see photo 2) it is clear that these were a huge mass of black tadpoles, apparently in their death throes as the pond dried. I immediately concluded they must be American toad tadpoles due to their color, choice of habitat, and time of year. Male American toads (see photo 3) start calling in early Spring when it rains and search out very small isolated ponds that lack fish and most other aquatic critters of any size. Their call is a series of long trills and it attracts females for mating. Long strings of eggs are laid and quickly hatch. Under ideal conditions the larvae grow rapidly and many will metamorphose at a very tiny size and leave the pond before it dries. However if enough rain does not fall to maintain the pond, all or most of the tadpoles may die, as seems to be the likely scenario here.

So why

would toads lay their eggs in such a difficult place to survive?

It seems completely counter-intuitive. Yet there is a method in this apparent madness- namely escape from the predation and competition in larger ponds. Only a few types of amphibians (such as bullfrogs and green frogs) are able to survive in ponds with fish. Amphibians such as spotted salamanders and wood frogs breed in fish-less temporary or vernal pools which may contain water for several months. The pools chosen by American toads are generally so small and temporary that few other amphibians and insects will breed there. This seems to be the strategy behind the strange choice of pools they make. Yet the shallow pools used by these toads would seem to make them very susceptible to predation by terrestrial and avian predators; their defense is to be toxic and to associate in large schools of their siblings. Thus when a foolish predator attacks a few tadpoles, it may then avoid eating any more in this group and those that survive are genetically related to the "martyrs."

So consider

the remarkable life history of the lowly toad and marvel at the complex interactions involved. Ain't Nature grand?

-Bill Dunson

What eggs are those?

On a visit to Chapel Hill on March 22 I was astonished at how many spotted salamander eggs/embryos were present in ponds of the area, especially in and near the UNC North Campus site.

If you are not too familiar with spotted salamanders eggs you may not realize that they can present a variety of patterns from clear, to greenish to milky white. The younger egg masses are clear or milky (the latter a variant with tiny crystals of protein in the jelly matrix for some as yet unknown reason). As they age a symbiotic green alga begins to grow inside the embryonic capsules and this is assumed to have a beneficial effect on supplying oxygen to the larvae.

An egg mass of a wood frog (from Grayson County, VA) is shown for comparison- in general they are clear and contain larger numbers of eggs per mass and the individual jelly capsules are more distinct. But they can also get quite greenish as they mature.

Since both of these species avoid ponds with fish they have relatively few places to breed in Grayson County. I think migrating shorebirds such as solitary and spotted sandpipers probably take a considerable toll of the hatched larvae if given an opportunity.

Bill Dunson

Galax, VA